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Short a straddle, then the stock gaps

Asked at SIG, Jane Street

You sell an at-the-money straddle at 30%30\% implied volatility with about 3030 days to expiry, and you delta-hedge it. For the first 2525 days the stock barely moves. Then on day 2626 it gaps 8%8\% overnight.

Walk through the P&L, and explain what this says about short-gamma risk and path dependence.

Your answer

This one is open-ended. Work it through, then check your reasoning against the full solution.

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